All of lore.kernel.org
 help / color / mirror / Atom feed
From: Xunlei Pang <xpang@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@arm.com>, Ingo Molnar <mingo@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH v3 1/6] rtmutex: Deboost before waking up the top waiter
Date: Mon, 18 Apr 2016 16:44:58 +0800	[thread overview]
Message-ID: <57149E8A.6060701@redhat.com> (raw)
In-Reply-To: <alpine.DEB.2.11.1604181018080.3941@nanos>

On 2016/04/18 at 16:23, Thomas Gleixner wrote:
> On Thu, 14 Apr 2016, Xunlei Pang wrote:
>> We should deboost before waking the high-prio task such that
>> we don't run two tasks with the 'same' priority.
> No. This is fundamentaly broken.
>  
> T1 (prio 0)	lock(X)
>
> -->	 	preemption
>
> T2 (prio 10)	lock(X)
>    	 	boost(T1)
> 		schedule()
>
> T1 (prio 10)	unlock(X)

We add a preempt_disable() before deboost to avoid the breakage,
there's also some comment about this in the patch's code.

Regards,
Xunlei

>    	 	deboost()
>    (prio 0) 
>
> -->		preemption
>
> T3 (prio 5)	....
>
> Classic priority inversion enabled by a mechanism to avoid it. Brilliant
> stuff.
>
> Thanks,
>
> 	tglx

  reply	other threads:[~2016-04-18  8:45 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-14 11:37 [PATCH v3 0/6] sched/deadline/rtmutex: Fix two deadline PI issues Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 1/6] rtmutex: Deboost before waking up the top waiter Xunlei Pang
2016-04-18  8:23   ` Thomas Gleixner
2016-04-18  8:44     ` Xunlei Pang [this message]
2016-04-18  9:02       ` Thomas Gleixner
2016-04-18  9:41         ` Xunlei Pang
2016-04-20 12:20         ` Peter Zijlstra
2016-04-20 12:43           ` Thomas Gleixner
2016-04-20 13:10             ` Peter Zijlstra
2016-04-14 11:37 ` [PATCH v3 2/6] sched/rtmutex/deadline: Fix a PI crash for deadline tasks Xunlei Pang
2016-04-20 13:19   ` Peter Zijlstra
2016-04-20 13:49     ` Xunlei Pang
2016-04-22  3:26       ` Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 3/6] rtmutex: Move "rt_mutex_waiter" definition to "include/linux/rtmutex.h" Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 4/6] sched: Move dl_policy() to "include/linux/sched.h" Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 5/6] sched/deadline/rtmutex: Fix unprotected PI access in enqueue_task_dl() Xunlei Pang
2016-04-14 15:31   ` Peter Zijlstra
2016-04-15  1:58     ` Xunlei Pang
2016-04-15  2:19       ` Xunlei Pang
2016-04-20 12:25         ` Peter Zijlstra
2016-04-20 13:00           ` Xunlei Pang
2016-04-20 13:17             ` Peter Zijlstra
2016-04-20 13:45               ` Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 6/6] sched/deadline/rtmutex: Don't miss the dl_runtime/dl_period update Xunlei Pang
2017-03-23 14:56 [PATCH -v3 0/8] PI vs SCHED_DEADLINE fixes Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 1/8] rtmutex: Deboost before waking up the top waiter Peter Zijlstra
2017-04-04  9:48   ` [tip:locking/core] " tip-bot for Xunlei Pang
2017-04-05  8:08     ` Mike Galbraith
2017-04-05 14:55       ` [tip:locking/core] Retiplockingcore_rtmutex_Deboost_before_waking_up_the_top_waiter tip-bot for Mike Galbraith
2017-04-05 15:03       ` [tip:locking/core] rtmutex: Plug preempt count leak in rt_mutex_futex_unlock() tip-bot for Mike Galbraith
2017-04-06  6:16       ` [tip:locking/core] rtmutex: Deboost before waking up the top waiter Xunlei Pang
2017-03-23 14:56 ` [PATCH -v3 2/8] sched/rtmutex/deadline: Fix a PI crash for deadline tasks Peter Zijlstra
2017-04-04  9:49   ` [tip:locking/core] " tip-bot for Xunlei Pang
2017-03-23 14:56 ` [PATCH -v3 3/8] sched/deadline/rtmutex: Dont miss the dl_runtime/dl_period update Peter Zijlstra
2017-04-04  9:50   ` [tip:locking/core] " tip-bot for Xunlei Pang
2017-03-23 14:56 ` [PATCH -v3 4/8] rtmutex: Clean up Peter Zijlstra
2017-03-23 18:21   ` Steven Rostedt
2017-04-04  9:50   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 5/8] sched/rtmutex: Refactor rt_mutex_setprio() Peter Zijlstra
2017-04-04  9:51   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 6/8] sched,tracing: Update trace_sched_pi_setprio() Peter Zijlstra
2017-04-04  9:51   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 7/8] rtmutex: Fix PI chain order integrity Peter Zijlstra
2017-04-04  9:52   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 8/8] rtmutex: Fix more prio comparisons Peter Zijlstra
2017-04-04  9:52   ` [tip:locking/core] " tip-bot for Peter Zijlstra

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=57149E8A.6060701@redhat.com \
    --to=xpang@redhat.com \
    --cc=juri.lelli@arm.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=rostedt@goodmis.org \
    --cc=tglx@linutronix.de \
    --cc=xlpang@redhat.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.